Journal of Alzheimer’s Disease

Neurocognitive disorders causing progressive cognitive, functional, and behavioral impairment remain underdiagnosed. The needs for a timely diagnosis are now widely acknowledged since person-centered care helps to preserve life quality and prevent crises. One powerful barrier to detection in primary care is the lack of an easy-to-follow stepwise approach, grounded in evidence and consistent with high-quality specialty practice. To help fill this gap, the current European Joint Action proposes a graduated diagnosis strategy tailored to the patients’ needs and wills, clarifying appropriate components for primary and specialty care. This strategy considers a first evaluation in primary care that may detect a neurocognitive disorder, that would lead to a second evaluation step allowing etiological diagnosis hypotheses performed mostly by the specialist. A third evaluation stage considering some biological, electrophysiological, or neuroimaging complementary techniques would be proposed to atypical cases or patients willing to consider access to research.

Alzheimer’s disease is the most common age-related neurodegenerative disorder and its burden on patients, families, and society grows significantly with lifespan. Early modifications of risk-enhancing lifestyles and treatment initiation expand personal autonomy and reduce management costs. Many clinical trials with potentially disease-modifying drugs are devoted to mild cognitive impairment (MCI) prodromal-to-Alzheimer’s disease. The identification of biomarkers for early diagnosis may thus be crucial for early intervention and identification of high-risk subjects, the most appropriate target of new drugs as soon as they will be discovered. INTERCEPTOR is a strategic project by the Italian Ministry of Health and the Italian Medicines Agency (AIFA), aiming to validate the best combination (highly accurate, non-invasive, available on the whole national territory and financially sustainable) of biomarkers and organizational model for early diagnosis. 500 MCI subjects will be enrolled at baseline and followed-up for 3 years for at least 400 of them in order to define a “hub & spoke” nationwide model with recruiting (spokes) centers for MCI identification and expert (hubs) centers for risk diagnosis.

Apolipoproteins (APOs) have been implicated in the pathogenesis of Alzheimer’s disease (AD). In the present study, we aimed to investigate if patterns of cerebrospinal fluid (CSF) APOs (APOA-I, APOC-III, APOD, APOE, APOH, and APOJ) levels are associated with changes over time in cognition, memory performance, neuroimaging markers, and AD-related pathologies (CSF Aβ₄₂, t-tau, and p-tau) in non-demented older adults. At baseline, a total of 241 non-demented older adults with CSF APOs data was included in the present analysis. Hierarchical agglomerative cluster analysis including the six CSF APOs was carried out. Among non-demented older adults, we identified two clusters. Compare with the first cluster, the second cluster had higher levels of APOs in CSF. Additionally, the second cluster showed a more benign disease course, including slower cognitive decline and slower p-tau accumulation in CSF. Our data highlight the importance of APOs in the pathogenesis of AD.

Ubiquitin Specific Protease-13 (USP13) is a de-ubiquinating enzyme that regulates protein ubiquitination and clearance. The role of USP13 is largely unknown in neurodegeneration. In this study we aim to demonstrate whether tau accumulation and/or clearance depends on ubiquitination/de-ubiquitination via USP-13. We used transgenic animal models of human amyloid precursor protein (APP) or P301L tau mutations and genetically knocked-down USP13 expression via shRNA to determine USP13 effects on tau ubiquitination and levels. We found a two-fold increase of USP13 levels in postmortem Alzheimer’s disease (AD) brains. USP13 knockdown significantly increased the activity of the 20S proteasome and reduced the levels of hyper-phosphorylated tau (p-tau) in primary cortical neurons. USP13 knockdown also reduced the levels of amyloid and increased p-tau ubiquitination and clearance in transgenic animal models that overexpress murine tau as a result of the expression of familial APP mutations (TgAPP) and the human mutant P301L tau (rTg4510), respectively. Clearance of p-tau appears to be mediated by autophagy in these animal models. Taken together, these data suggest that USP13 knockdown reduces p-tau accumulation via regulation of ubiquitination/de-ubiquitination and mediates its clearance via autophagy and/or the proteasome. These results suggest that USP13 inhibition may be a therapeutic strategy to reduce accumulation of plaques and toxic p-tau in AD and human tauopathies.

Diffusion changes as determined by diffusion tensor imaging are potential indicators of microstructural lesions in people with mild cognitive impairment (MCI), prodromal Alzheimer’s disease (AD), and AD dementia. Here we extended the scope of analysis toward subjective cognitive complaints as a pre-MCI at risk stage of AD. In a cohort of 271 participants of the prospective DELCODE study, including 93 healthy controls and 98 subjective cognitive decline (SCD), 45 MCI, and 35 AD dementia cases, we found reductions of fiber tract integrity in limbic and association fiber tracts in MCI and AD dementia compared with controls in a tract-based analysis (p < 0.05, family wise error corrected). In contrast, people with SCD showed spatially restricted white matter alterations only for the mode of anisotropy and only at an uncorrected level of significance. DTI parameters yielded a high cross-validated diagnostic accuracy of almost 80% for the clinical diagnosis of MCI and the discrimination of Aβ positive MCI cases from Aβ negative controls. In contrast, DTI parameters reached only random level accuracy for the discrimination between Aβ positive SCD and control cases from Aβ negative controls. These findings suggest that in prodromal stages of AD, such as in Aβ positive MCI, multicenter DTI with prospectively harmonized acquisition parameters yields diagnostic accuracy meeting the criteria for a useful biomarker. In contrast, automated tract-based analysis of DTI parameters is not useful for the identification of preclinical AD, including Aβ positive SCD and control cases.

Hippocampal lesions including synaptic injury, neuroinflammation, and impaired neurogenesis are featured pathology closely associated with neuronal stress and cognitive impairment in Alzheimer’s disease (AD). Previous studies suggest that ghrelin and its receptor, growth hormone secretagogue receptor 1α (GHSR1α), promote hippocampal synaptic function and neurogenesis. GHSR1α activation thus holds the potential to be a therapeutic avenue for the treatment of hippocampal pathology in AD; however, a comprehensive study on the preventive effect of MK0677 on hippocampal lesions in AD-related conditions is still lacking. In this study, we treated a transgenic mouse model of AD-like amyloidosis (5xFAD mice) at the asymptomatic stage with MK0677, a potent ghrelin mimetic. We found that MK0677 fostered hippocampal neurogenesis in 5xFAD mice but observed little preventive function with regards to the development of hippocampal amyloid-β (Aβ) deposition, synaptic loss, microglial activation, or cognitive impairment. Furthermore, MK0677 at a dose of 3 mg/kg significantly increased 5xFAD mouse mortality. Despite enhanced hippocampal neurogenesis, MK0677 treatment has little beneficial effect to prevent hippocampal lesions or cognitive deficits against Aβ toxicity. This study, together with a failed large-scale clinical trial, suggests the ineffectiveness of MK0677 alone for AD prevention and treatment.

Abnormal accumulation of amyloid-β (Aβ) in the brain is the most significant pathological hallmark of Alzheimer’s disease (AD). We have found that chronic systemic exposure to lipopolysaccharide of Porphyromonas gingivalis (P. gingivalis) induces the accumulation of Aβ in the brain of middle-aged mice. On the other hand, recent research has shown that circulating Aβ is transferred into the brain; however, the involvement of chronic systemic P. gingivalis infection in the peripheral Aβ metabolism is unknown. We hypothesized that chronic P. gingivalis infection expands Aβ pools in peripheral inflammatory tissues and thereby contributes to the accumulation of Aβ in the brain of patients with periodontitis. We showed that the increased expression of IL-1β, AβPP₇₇₀, CatB, Aβ_1-42, and Aβ_3-42 was mainly co-localized with macrophages in the liver of P. gingivalis infected mice. Blocking CatB and NF-κB significantly inhibited the P. gingivalis-induced expression of IL-1β, AβPP₇₇₀, Aβ_1-42, and Aβ_3-42 in RAW264.7 cells. Aβ_3-42, but not Aβ_1-42, induced the significant death of macrophages, and the reduction of phagocytic abilities induced by Aβ_3-42 tended to be higher than that induced by Aβ_1-42. Additionally, the expression of AβPP₇₇₀, CatB, Aβ_1-42, and Aβ_3-42 was determined in the macrophages of gingival tissues from periodontitis patients. These findings indicate that chronic systemic P. gingivalis infection induces the Aβ accumulation in inflammatory monocytes/macrophages via the activation of CatB/NF-κB signaling, thus suggesting monocytes/macrophages serve as a circulating pool of Aβ in patients with periodontitis. Taken together, CatB may be a novel therapeutic target for preventing the periodontitis-related AD initiation and pathological progression.

In this research work, machine learning techniques are used to classify magnetic resonance imaging brain scans of people with Alzheimer’s disease. This work deals with binary classification between Alzheimer’s disease and cognitively normal. Supervised learning algorithms were used to train classifiers in which the accuracies are being compared. The database used is from The Alzheimer’s Disease Neuroimaging Initiative (ADNI). Histogram is used for all slices of all images. Based on the highest performance, specific slices were selected for further examination. Majority voting and weighted voting is applied in which the accuracy is calculated and the best result is 69.5% for majority voting.

Observations in autopsied brain tissue indicate that overactivation of the classical renin-angiotensin system (cRAS) and underactivity within regulatory RAS pathways (rRAS) are associated with pathology in Alzheimer’s disease (AD). The primary aim of this study was to investigate whether cerebrospinal fluid (CSF) markers of RAS are altered in AD in relation to established CSF markers of disease pathology (lower Aβ₄₂ and elevated tau) and CSF markers of capillary dysfunction. We studied 40 controls and 40 AD cases grouped according to a biomarker profile (i.e., AD cases t-tau>400 pg/mL, pTau >60 pg/mL, and Aβ₄₂ <550 pg/mL). Angiotensin-II converting enyme-1 (ACE1) and ACE2 enzyme activity was measured using fluorogenic peptide substrates; sPDGFRβ and albumin level by sandwich ELISA; and angiotensin-I (Ang-I), Ang-II, and Ang-(1-7) by direct ELISA. CSF Aβ₄₂, total, and phosphorylated tau levels were previously measured by INNOTEST sandwich ELISA. CSF ACE1 activity was significantly elevated in AD (p = 0.008) and positively correlated with ACE2 in AD (r = 0.420, p = 0.007). CSF ACE1 weakly correlated with t-tau (r = 0.294, p = 0.066) and p-tau (r = 0.329, p = 0.038) but not with Aβ₄₂ in the controls but not in AD. ACE1 correlated positively with sPDGFRβ (r = 0.426, p = 0.007), a marker of pericyte injury, and ACE2 correlated positively with albumin (r = 0.422, p = 0.008), a marker of blood-brain barrier integrity. CSF Ang-I, Ang-II, and Ang-(1-7) levels were unchanged in AD. This cross-sectional CSF study indicates RAS dysfunction in relation to capillary damage in AD.

The amyloid-β protein precursor (AβPP) is critical in the pathophysiology of Alzheimer’s disease (AD), since two-step proteolytic processing of AβPP generates the neurotoxic amyloid-β peptide (Aβ). We developed a dual fluorescence labeling system to study the exact subcellular location of γ-secretase cleavage of AβPP. The C-terminal tail of AβPP was fluorescently labeled using a SNAP-tag, while the Aβ region of AβPP was fluorescently tagged with a dye at a genetically-encoded noncanonical amino acid (ncAA). The ncAA was introduced at specific positions in AβPP using a genetic code expansion strategy and afterwards, the reactive side-chain of the ncAA was coupled to the dye using a bioorthogonal labeling chemistry. In proof-of-concept experiments, HEK293T cells were transfected with plasmids containing engineered AβPP harboring an amber mutation and an amber codon suppression system with an evolved tRNA synthetase/tRNA pair and grown in the presence of a lysine-derived ncAA. Processing of the AβPP variants was validated with ELISA and immunoblotting, and seven AβPP mutants that showed similar cleavage pattern as wild-type AβPP were identified. The AβPP mutant was fluorescently labeled with 6-methyl-tetrazine-BDP-FL and TMR-Star at the ncAA and SNAP-tag, respectively. Using this approach, AβPP was fluorescently labeled at two sites in living cells with minimal background to allow monitoring of Aβ and C-terminal cleavage products simultaneously. The method described provides a powerful tool to label Aβ with minimal perturbations of its processing, thus enabling studies of the trafficking of the cleavage products of AβPP.

The use of existing public spaces by people living with dementia, such as museums and art galleries, are becoming popular due to their ability to facilitate programs which promote social engagement and inclusion. However, few studies have investigated physiological outcomes of art gallery-based programs. Using a quasi-experimental design, the present study aimed to investigate the levels of salivary biomarkers of cortisol and interleukin-6, quality of life (QoL), depressive symptoms, cognition, and wellbeing, after attending the National Gallery of Australia (NGA) Art and Dementia program. Twenty-eight people living with dementia, each supported by a carer or family member, were recruited for a six-week program and were followed up at twelve weeks. In total, 25 participants (17 female; mean age 84.6±7.27 years) completed the study, and 22 provided viable saliva samples. The waking to evening salivary cortisol ratio was higher post-intervention (p = 0.033), and returned to baseline levels at follow-up (p = 1.00), indicating a more dynamic salivary cortisol rhythm in response to the six-week program. Interleukin-6 levels remained unchanged (p = 0.664). No improvements in QoL (DEMQOL-Carer) were observed between baseline and post-intervention (p = 0.076). However, self-reported depressive symptoms decreased post-intervention compared with baseline (p = 0.015), and memory (immediate recall) (p = 0.009) and verbal fluency (p = 0.027) improved between the same timepoints. The NGA Art and Dementia program appears to have quantifiable benefits, including improved hypothalamic-pituitary-adrenal axis function, justifying a need for longer controlled trial inclusive of physiological outcomes.

Engaging in meaningful and enjoyable activities is an important contributor to well-being and maintaining good quality of life. There is a paucity of randomized controlled trials of interventions supporting people with mild dementia to engage in meaningful and purposeful activity. The aim of this study was to assess whether Behavioral Activation (BA) is an acceptable psychological intervention for people with mild dementia and whether a large-scale trial is feasible. Participants were randomly assigned to BA (n = 42) or treatment as usual (TAU) (n = 21). BA aimed at increasing engagement in enjoyable and meaningful activity, and preventing low mood. Follow-up was at 3 and 6 months. Assessors were blind to treatment allocation (trial registration number: ISRCTN75503960). Retention rate was above 80% at both assessment time points. Treatment acceptability and credibility were high. Depressive symptoms remained unchanged in both groups. There was evidence of improvement associated with BA for every day function (–3.92, 95% Confidence Interval (CI) –6.87 to –0.97), and engagement in meaningful and enjoyable activity (5.08, 95% CI 0.99 to 9.16) post-treatment (3 months) in comparison to TAU. Both carer-rated patient health-related quality of life (0.16, 95% CI 0.04 to 0.28) and physical health (11.31, 95% CI 2.03 to 20.59) showed evidence of improvement at 3 months. Improvements in meaningful and enjoyable activity were maintained at 6 months.

BA for people with mild dementia is feasible and acceptable and may be associated with clinically significant changes in function and quality of life. A full scale randomized controlled trial of clinical effectiveness is now needed.

Extracellular vesicles (EVs) are a heterogeneous group of secreted particles consisting of microvesicles, which are released by budding of the cellular membrane, and exosomes, which are secreted through exocytosis from multivesicular bodies. EV cargo consists of a wide range of proteins and nucleic acids that can be transferred between cells. Importantly, EVs may be pathogenically involved in neurodegenerative diseases such as Alzheimer’s disease (AD). While EVs derived from AD neurons have been found to be neurotoxic in vitro, little is known about the pathological consequences of AD EVs in vivo. Furthermore, although all known familial AD (fAD) mutations involve either amyloid-β protein precursor (AβPP) or the machinery that processes AβPP, hyperphosphorylation of the microtubule associated protein tau appears to play a critical role in fAD-associated neurodegeneration, and previous reports suggest EVs may propagate tau pathology in the AD brain. Therefore, we hypothesized that fAD EVs may have a mechanistic involvement in the development of fAD-associated tau pathology. To test this, we isolated EVs from iPSC-derived neuronal cultures generated from an fAD patient harboring a A246E mutation to presenilin-1 and stereotactically injected these EVs into the hippocampi of wild-type C57BL/6 mice. Five weeks after injection, mice were euthanized and pathology evaluated. Mice injected with fAD EVs displayed increased tau phosphorylation at multiple sites relative to PBS and non-disease control EV injected groups. Moreover, fAD EV injected hippocampi contained significantly more tau inclusions in the CA1 hippocampal neuronal field than controls. In total, these findings identify EVs as a potential mediator of fAD-associated tau dysregulation and warrant future studies to investigate the therapeutic potential of EV-targeted treatments for fAD.

Pathogenesis of neurodegenerative diseases involves dysfunction of mitochondria, one of the most important cell organelles in the brain, with its most prominent roles in producing energy and regulating cellular metabolism. Here we investigated the effect of transferring active intact mitochondria as a potential therapy for Alzheimer’s disease (AD), in order to correct as many mitochondrial functions as possible, rather than a mono-drug related therapy. For this purpose, AD-mice (amyloid-β intracerebroventricularly injected) were treated intravenously (IV) with fresh human isolated mitochondria. One to two weeks later, a significantly better cognitive performance was noticed in the mitochondria treated AD-mice relative to vehicle treated AD-mice, approaching the performance of non-AD mice. We also detected a significant decrease in neuronal loss and reduced gliosis in the hippocampus of treated mice relative to untreated AD-mice. An amelioration of the mitochondrial dysfunction in brain was noticed by the increase of citrate-synthase and cytochrome c oxidase activities relative to untreated AD-mice, reaching activity levels of non-AD-mice. Increased mitochondrial activity was also detected in the liver of mitochondria treated mice. No treatment-related toxicity was noted. Thus, IV mitochondrial transfer may possibly offer a novel therapeutic approach for AD.

Recent studies found that poor oral hygiene was associated with increased risk of dementia, and the number of oral bacteria significantly increased in the brain tissues of patients with Alzheimer’s disease (AD), suggesting that the oral microbiota may play an important role in the pathogenesis of AD. However, the actual composition of oral bacteria communities in patients with AD and whether these oral bacteria are associated with disease severity remain largely unknown. Also, the APOE ɛ4 polymorphism is a strong risk factor for sporadic AD, and it would be pertinent to see if the bacterial flora was different in those patients who were APOE ɛ4 positive. A total of 78 subjects were recruited in this study, including 39 patients with AD and 39 healthy controls. Saliva was collected from each subject. 16S ribosomal RNA (16S rRNA) sequencing was conducted to analyze the salivary microbiota, and Sanger sequencing was performed to analyze the APOE genotype. There was a significantly lower richness and diversity of saliva microbiota detected in AD patients than healthy controls. The relative abundance of Moraxella, Leptotrichia, and Sphaerochaeta in the saliva of AD patients greatly increased, whereas that of Rothia was significantly reduced. Compared with APOE ɛ4 (–) patients, the level of Abiotrophia and Desulfomicrobium was comparatively abundant, while Actinobacillus and Actinomyces decreased significantly in patients carrying the APOE ɛ4. No bacteria were found to be associated with the severity of AD. This is the first study to analyze the salivary microorganisms in patients with AD, and we discovered that the composition of salivary microbiome was altered in AD, providing further support for the role of the oral microbiome in AD development.